Organosolv delignification and saccharification process for lignocellulosic plant materials

Abstract

Cellulose-containing material is rapidly saccharified to convert pentosans and hexosans to sugars by cooking under pressure at from 180 DEG C. to 220 DEG C. with acetone-water solvent mixture carrying from 0.05 to 0.25 weight percent of phosphoric, sulfuric or hydrochloric acids. A predominantly cellulosic material, e.g. a delignified pulp, is hydrolysed to yield relatively pure glucose recoverable from liquor which is flowed through the cellulose, then withdrawn and cooled and neutralized within an elapsed time of a minute or less. Whole wood is nearly totally dissolvable by the process, yielding mixed pentoses and hexoses. The dehydration and degradation products of sugars are formed by prolonging retention time of liquor from 20 to 45 minutes.

We claim: 
     
       1. In a process for the production of carbohydrate hydrolysates of cellulose from a cellulosic material which can contain lignin by treating the material in a pressure vessel with a solvent mixture with water containing a small quantity of a mineral acid selected from the group consisting of hydrochloric, sulfuric and phosphoric acids at an elevated temperature to solubilize the carbohydrate and until sugars are formed by hydrolysis from the solubilized carbohydrate in a liquor the improvement which comprises the steps of: (a) supplying a solvent mixture containing acetone and water in a volume ratio of acetone to water between 70 to 30 and 60 to 40 and the acid in an amount of between 0.05 and 0.25 percent by weight of the mixture of hydrochloric acid or between 0.15 and 0.25 percent by weight of the mixture of phosphoric or sulfuric acids into the vessel under pressure with the cellulosic material to provide a limited retention time of the solvent mixture in the vessel of seven minutes or less such that sugars are not dehydrated or degraded into non sugars and then removing the solvent mixture as the liquor containing the sugars wherein the liquor removed from the vessel initially contains lignin and is separated from the liquor collected subsequently which contains the sugars;   (b) rapidly cooling the liquor immediately upon removal from the vessel to prevent degradation of the sugars to non sugars;   (c) recovering the sugars from the cooled liquor.   
     
     
       2. The process of claim 1 wherein the cellulosic material is a pulp. 
     
     
       3. The process of claim 1 wherein the liquor is continuously removed and cooled and fresh solvent mixture is supplied into the vessel so that sugars are exposed to heat for seven minutes or less. 
     
     
       4. The process of claim 1 wherein the withdrawn liquor is evaporated to separate acetone as a vapour from the aqueous liquor, and the vapour is condensed and recycled. 
     
     
       5. The process of claim 1 wherein the process is stopped at the time when a microcrystalline residue remains. 
     
     
       6. In a process for the production of carbohydrate hydrolysates and lignins from a lignocellulosic material, by treating the material in a pressure vessel with a solvent mixture with water containing a small quantity of an acid selected from the group consisting of hydrochloric, sulphuric and phosphoric acids at an elevated temperature to solubilize the carbohydrate and lignins and until sugars are formed in solubilized form in a liquor the improvement which comprises the steps of: (a) supplying a solvent mixture containing the acid in an amount between 0.05 and 0.25 percent by weight of the mixture of hydrochloric acid or between 0.15 and 0.25 percent by weight of the mixture of sulfuric or phosphoric acids, water and acetone in a volume ratio of acetone to water of between 70 to 30 and 60 to 40 into the vessel under pressure to provide a limited retention time of the solvent mixture in the vessel of seven minutes or less and then removing the solvent mixture as the liquor, wherein the liquor collected initially from the vessel contains the lignin and is separated from liquor collected subsequently after the liquor with the lignin is removed which contains the sugars, and wherein the sugars from the hydrolysis are not dehydrated or degraded into non-sugars;   (b) rapidly cooling the hydrolysis liquors as they are removed from the vessel to prevent degradation of sugars to non sugars by removing the acetone wherein the lignins in the liquor collected initially are precipitated by the removal of the acetone;   (c) removing the precipitated lignin from the hydrolysis liquor collected initially; and   (d) recovering the sugars from the hydrolysis liquors collected initially and subsequently.